Turbine systems are widely used in fields such as power generation and aviation. A typical gas turbine includes a compressor section, a combustion section downstream from the compressor section, and a turbine section that is downstream from the combustion section. At least one shaft extends axially at least partially through the gas turbine. A generator/motor may be coupled to the shaft at one end. The combustion section generally includes a casing and a plurality of combustors arranged in an annular array around the casing. The casing at least partially defines a high pressure plenum that surrounds at least a portion of the combustors.
In operation, compressed air is routed from the compressor section to the high pressure plenum that surrounds the combustors. The compressed air is routed to each of the combustors where it is mixed with a fuel and combusted. Combustion gases having a high velocity and pressure are routed from each combustor through one or more liners, through a first stage of stationary nozzles or vanes and into the turbine section where kinetic and/or thermal energy from the hot gases of combustion is transferred to a plurality of rotatable turbine blades which are coupled to the shaft. As a result, the shaft rotates, thereby producing mechanical work. For example, the shaft may drive the generator to produce electricity.
Each combustor includes an end cover that is coupled to the casing. At least one fuel nozzle extends axially downstream from the end cover and at least partially through a cap assembly that extends radially within the combustor. An annular liner such as a combustion liner or a transition duct extends downstream from the cap assembly to at least partially define a combustion chamber within the casing. The liner at least partially defines a hot gas path for routing the combustion gases through the high pressure plenum towards an inlet of the turbine section. An aft frame or support frame circumferentially surrounds a downstream end of the liner, and a bracket is coupled to the aft frame for mounting the liner. The aft frame terminates at a point that is generally adjacent to a first stage nozzle which at least partially defines the inlet to the turbine section.
In some gas turbines, the liner and the first stage nozzle are mounted to a common inner support ring and/or a common outer support ring. In this manner, relative motion between the liner and the first stage nozzle is minimized as the gas turbine transitions through various thermal transients such as during startup and/or turndown operation of the gas turbine. Although this mounting scheme is effective, it is necessary to leave a gap between the aft frame and/or the liner and the first stage nozzle to allow for thermal growth and/or movement of the liner and/or the first stage nozzle as the gas turbine transitions through the various thermal transients.
The size of the gap is generally important for at least two reasons. First, the gap must be sufficient to prevent contact between the aft frame and the first stage nozzle during operation of the gas turbine. Second, the gap must be as small as possible to prevent a portion of the high pressure combustion gases from leaking from the hot gas path through the gap and into the high pressure plenum, thereby impacting the overall performance and/or efficiency of the gas turbine. As a result, seals are required to reduce and/or to seal the gap.
In particular gas turbines, the turbine section includes both an outer turbine shell and an inner turbine shell. In this configuration, the liner is coupled to the inner support ring and the first stage nozzle is coupled and/or in contact with both the inner support ring and the inner turbine shell. Generally, the inner turbine shell is constrained at an aft end of the turbine section, and the inner support ring is mounted to a separate structure. As a result, the inner turbine shell and the inner support ring tend to translate and grow thermally in different directions which results in an increase in relative motion between the liner and the first stage nozzle as compared to when the liner and the first stage nozzle are mounted to common inner and/or outer support rings.
The relative motion between the liner and the first stage nozzle requires a large gap between the aft frame and the first stage nozzle to prevent contact between the two components during operation of the gas turbine. As a result, larger seals must be developed to reduce or prevent leakage of the combustion gases from the hot gas path. However, uncertainties in the motion of the components as well as high temperatures tend to limit the life and/or the effectiveness of the seals. Therefore, an assembly which controls and/or minimizes a gap size or clearance between a liner and a stationary nozzle within a gas turbine having an inner and an outer turbine shell during various thermal transients would be useful.